Firefighters inspect a burned over ridge from the Yarnell Hill Fire near Peeples Valley, Ariz., on Wednesday, July 3, 2013. / David Wallace, The Arizona Republic

by Yvonne Wingett Sanchez and Dennis Wagner, The Arizona Republic

by Yvonne Wingett Sanchez and Dennis Wagner, The Arizona Republic

PHOENIX -- An investigative report on the Yarnell Hill Fire that killed 19 members of the Granite Mountain Hotshots firefighting team is scheduled to be released at a news conference Saturday morning in Prescott.

The report is expected to provide an account of the fatal accident, along with recommendations to avoid similar tragedies.

The Arizona State Forestry Division commissioned an interagency task force of experts to investigate causes of and contributing factors to the June catastrophe.

Officials are expected to brief the Hotshots' family members shortly before the findings are released publicly.

The Hotshot team was overcome by flames June 30 in a chaparral canyon about 35 miles south of Prescott when the fire, pushed by monsoon-storm winds, changed direction and became a fast-moving inferno. The death toll was the highest from a U.S. wildfire in at least a half-century. Only one member of the crew, who was serving as a lookout, survived the blaze.

The review team, led by Florida forester Jim Karels, is expected to discuss how it conducted its investigation. The team likely will address whether it is adhering to guidelines set by the National Interagency Fire Center that urge investigators to withhold the causes of wildfire accidents.

Some wildfire experts say that if the team follows those guidelines, the public is unlikely to get a clear understanding of what went wrong or what can be done to prevent future tragedies.

Public-relations practitioners questioned the unusual Saturday-morning timing of a news conference that has significant national interest.

"If they're trying to jockey things to get out of a news cycle, the backfire could be a mega-story all weekend," said Ross Johnson, a crisis-management specialist in Los Angeles.

Johnson, who has relatives in the Prescott area, said there seems to be a culture of opaqueness when it comes to accident investigations in wildfire communities, where survivors want to protect the "hero legend" narrative of those who died.

"Yes, this was cataclysmic," he added. "But other firefighters need to know the truth" about what happened.

Jonathan Bernstein, president of a California crisis-management firm and author of a book on the topic, said the Saturday-morning timing might have dampened coverage in the pre-Internet era, but with today's 24-hour news cycle, a report on 19 firefighter deaths might get even more play over a weekend.

"It's strange timing," he said. "(But) there's going to be interest in this story no matter when it gets released."

Lightning ignited the Yarnell Hill Fire on June 28, and it remained seemingly calm for two days before a storm front descended and pushed a wall of flames through drought-dry hills at 12 mph. A relatively small brush fire that covered only a few hundred acres quickly exploded across 13 square miles and swept into rural communities.

Hundreds of people were evacuated from the communities of Yarnell, Glen Ilah and Peeples Valley as flames destroyed 127 homes.

The Hotshots, who had been hand-cutting firebreaks along the blaze's flank, were forced to retreat.

Photographic evidence indicates they left the safety of a previously burned area and descended into a blind valley, where they were trapped by flames.

The 19 men deployed protective shelters in a desperate bid to survive but were overcome by a wall of fire so hot that it fractured boulders and incinerated vegetation.

In addition to the Serious Accident Investigation, the Arizona Division of Occupational Safety and Health is conducting a probe to determine whether workplace regulations were violated. That report must be completed by the end of the year.